Note that the pygame coordinate system (and most other graphics libraries too) places the origin in the upper left corner, has an x-axis that runs horizontally to the right, and a y-axis that runs vertically downward.
This means that a pygame coordinate (x,y) refers to column x and row y which is the opposite of the way lists of lists are addressed which is (row, column) and yes this irritating and leads to bugs, so be aware!